In recent years, in a solid-state imaging apparatus such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, miniaturization of pixel size has been under way. This causes a reduction in the number of photons entering a unit pixel, thus resulting in reduced sensitivity and a lower S/N ratio. In addition, in a case where a color filter including two-dimensionally arranged primary color filters of red, green, and blue is used for colorization, green light and blue light are absorbed by the color filter in a red pixel, for example, thus leading to the reduced sensitivity. Moreover, upon generation of a signal of each color, interpolation processing is performed between the pixels, thus generating a false color.
Hence, for example, PTL 1 discloses an image sensor using an organic photoelectric conversion film having a multilayer structure in which an organic photoelectric conversion film having sensitivity to blue light (B), an organic photoelectric conversion film having sensitivity to green light (G), and an organic photoelectric conversion film having sensitivity to red light (R) are sequentially stacked. In this image sensor, sensitivity is improved by separate extraction of signals of B/G/R from one pixel. PTL 2 discloses an imaging element in which a single-layer organic photoelectric conversion film is formed, a signal of one color is extracted in the organic photoelectric conversion film, and signals of two colors are extracted through silicon (Si) bulk spectroscopy.
In such an imaging element that extracts the signals of the two colors through the Si bulk spectroscopy and extracts the signal of the one color in the organic photoelectric conversion film provided on a Si bulk, the organic photoelectric conversion film is formed with a combination of two kinds of materials, for example. In PTL 3 and PTL 4, for example, fullerenes, subphthalocyanines, and quinacridones are used in combination.